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Finding the Fourth Proportional to 1,387.64, 1,915.02 and 921.56

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Solution

The fourth proportional to 1,387.64, 1,915.02 and 921.56 is: 1,271.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,387.64 : 1,915.02 = 921.56 : x
  2. Step 2: Convert to fraction form
    1,387.64/1,915.02 = 921.56/x
  3. Step 3: Cross multiply
    1,387.64x = 1,915.02 × 921.56
  4. Step 4: Simplify right side
    1,387.64x = 1,764,805.83
  5. Step 5: Solve for x
    x = 1,764,805.83/1,387.64
  6. Step 6: Final answer
    x = 1,271.80

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.